Unable to use galleries shortcode or Tiled Galleries plugin via Jetpack

I’m trying to add galleries to a couple of our pages. The galleries shortcode doesn’t work (nothing displays except the shortcode text) and when we installed the Tiled Galleries plugin via the Jetpack, there was no option to display images as a mosaic under Settings -> Media. (The theme was activated).

I’ve researched this a bit and suspect it’s an issue with our theme or a conflicting plugin, but I can’t find the exact issue and don’t know enough code to get very deep into our site. Would appreciate any help or tips! We are running the Churchope theme.